JPWO2018124084A1 - Chemically strengthened glass plate and method for producing chemically strengthened glass plate - Google Patents

Abstract

The glass plate for chemical strengthening of the present invention has a thickness of 0.4 mm or more and less than 1.0 mm, and has a Vickers hardness higher than 500 and lower than 650 when immersed in KNO3 molten salt at 430 ° C. for 4 hours. The resulting surface compressive stress layer has a compressive stress value of 1100 MPa or more and less than 1500 MPa, and a Vickers hardness of 700 or more and less than 1100.

Description

  TECHNICAL FIELD The present invention relates to a chemically strengthened glass plate and a method for producing a chemically strengthened glass plate, and in particular, a chemically strengthened glass plate and a chemically strengthened glass plate suitable for a cover glass of a mobile phone, a digital camera, a PDA (mobile terminal), and a touch panel display. It relates to the manufacturing method.

  Mobile phones, digital cameras, PDAs, and touch panel displays are becoming increasingly popular. For these uses, a chemically strengthened glass plate subjected to ion exchange treatment is used as a cover glass (see Patent Document 1 and Non-Patent Document 1).

JP 2006-83045 A JP-T-2006-524581 Special table 2011-510903 gazette

Tetsuro Izumiya et al., “New Glass and its Properties”, first edition, Management System Laboratory, Inc., August 20, 1984, p. 451-498

  Since cover glasses, particularly smartphone cover glasses, are often used outdoors, surface scratches are easily recognized by light having high illuminance and parallelism, and the visibility of the display is reduced. Therefore, it is important to improve the scratch resistance of the chemically strengthened glass plate.

  As a method for improving scratch resistance, it is considered useful to increase the hardness of glass. More specifically, the conventional glass has a property that the surface is easily scratched due to the silica because the hardness is significantly lower than that of silica (silica sand) that exists a lot on the ground. Therefore, it is considered that when the hardness of the glass is increased, the surface is hardly damaged. However, when the hardness of the glass is increased, it becomes difficult to perform cutting processing, end surface processing, or the like to a predetermined size before the ion exchange treatment, which may increase the processing cost.

  Further, it is known that when a hard thin film is formed on the glass surface, the hardness of the cover glass is increased (see, for example, Patent Document 2). However, when a hard thin film is formed on the glass surface, the transparency of the cover glass may decrease, or the cover glass may be warped due to film stress.

  In addition, since sapphire has high hardness, it seems that it is suitable for a cover member. However, sapphire is difficult to mass-produce large-sized plates.

  The present invention has been made in view of the above circumstances, and the technical problem thereof is a glass plate for chemical strengthening and chemical strengthening that have good workability before ion exchange treatment and are less likely to be scratched after ion exchange treatment. The idea is to create a glass plate manufacturing method.

As a result of various studies by the present inventors, paying attention to Vickers hardness as an index of scratch resistance, if the Vickers hardness before ion exchange treatment is low and the Vickers hardness after ion exchange treatment is high, the above technical problem is The present invention has been found out that the problem can be solved, and is proposed as the present invention. That is, the chemically strengthened glass plate of the present invention has a plate thickness of 0.4 mm or more and less than 1.0 mm, a Vickers hardness higher than 500 and lower than 650, and a KNO ₃ molten salt at 430 ° C. for 4 hours. When immersed, the surface compressive stress layer obtained has a compressive stress value of 1100 MPa or more and less than 1500 MPa, and a Vickers hardness of 700 or more and less than 1100. Here, the Vickers hardness indicates a value measured based on a method based on JIS Z2244 with a measurement load of 100 gf. In addition, the “compressive stress value of the surface compressive stress layer” and the “stress depth of the surface compressive stress layer” are determined when the sample is observed using a surface stress meter (for example, FSM-6000 manufactured by Toshiba Corporation). A value calculated from the number of observed interference fringes and their intervals.

  Conventionally, the scratch resistance has been evaluated by the degree of occurrence of cracks caused by the indentation of a Vickers indenter or the degree of occurrence of lateral cracks caused by scratching of the Knoop indenter (see Patent Document 3). However, the crack generation mechanism differs between the crack generated in the above evaluation and the surface scratch recognized by light having high illuminance and parallelism. Therefore, even if the glass is less prone to crack in the conventional evaluation, surface scratches recognized by light having high illuminance and parallelism may occur, and the above technical problem may not be solved.

According to the inventors' investigation, the degree of occurrence of surface scratches recognized by light with high illuminance and parallelism has a correlation with Vickers hardness, and if the Vickers hardness after ion exchange treatment is increased, the surface scratches are reduced. can do. Therefore, the glass plate for chemical strengthening of the present invention is characterized by having a Vickers hardness of 700 or more when immersed in KNO ₃ molten salt at 430 ° C. for 4 hours. However, if the Vickers hardness is extremely increased, the workability before the ion exchange treatment may be significantly reduced. Therefore, the glass plate for chemical strengthening of the present invention regulates the Vickers hardness before ion exchange treatment to less than 650.

According to the inventors' investigation, when a large amount of Al ₂ O ₃ , Li ₂ O, MgO, CaO, ZrO ₂ , Y ₂ O ₃ , La ₂ O _3, etc. is introduced into the glass composition, Vickers before the ion exchange treatment It becomes easy to increase hardness. Further, when the compressive stress value of the surface compressive stress layer is increased, the Vickers hardness after the ion exchange treatment is easily increased.

Further, chemically tempered glass plate of the present invention, when immersed for 4 hours in KNO ₃ molten salt at 430 ° C., it is preferred that the stress depth of resulting surface compressive stress layer is less than 100 [mu] m.

  Moreover, it is preferable that at least one surface of the glass plate for chemical strengthening of the present invention is a polished surface.

  Moreover, it is preferable that the glass plate for chemical strengthening of this invention has an overflow merge surface in the center part of a plate | board thickness direction. That is, it is preferably formed by an overflow downdraw method.

Further, chemically tempered glass plate of the present invention has a glass composition, in _{mol%, SiO 2 50~80%, Al} 2 O 3 12~18%, containing Na 2 O 12 to 20%, molar ratio Na ₂ O / Al ₂ O ₃ is preferably 0.9 to 1.5.

  The method for producing a chemically strengthened glass plate according to the present invention includes forming a molten glass into a plate shape and then cutting it into a predetermined size, whereby the plate thickness is 0.4 mm or more and less than 1.0 mm, and the Vickers hardness is The glass plate preparation step for obtaining a glass plate for chemical strengthening higher than 500 and lower than 650, and the glass plate for chemical strengthening are subjected to ion exchange treatment, and the compressive stress value of the surface compressive stress layer is 1100 MPa or more and less than 1500 MPa. And an ion exchange treatment step for obtaining a chemically strengthened glass plate having a Vickers hardness of 700 or more and less than 1100.

  Moreover, it is preferable that the manufacturing method of the chemically strengthened glass plate of this invention ion-exchange-processes the glass plate for chemical strengthening, and obtains the chemically strengthened glass plate whose stress depth of a surface compressive-stress layer is less than 100 micrometers.

  Moreover, it is preferable that the manufacturing method of the chemically strengthened glass plate of this invention is further equipped with the grinding | polishing process which grind | polishes at least one surface of the glass plate for chemical strengthening.

  In the method for producing a chemically strengthened glass sheet of the present invention, the temperature range between the annealing point and strain point of the chemically strengthened glass sheet (molten glass) is 3 ° C./min or more and 1000 It is preferable to cool at a cooling rate of less than ° C / min. Here, “strain point” and “annealing point” refer to values measured based on the method of ASTM C336.

  Moreover, it is preferable that the manufacturing method of the chemically strengthened glass plate of this invention shape | molds molten glass by the overflow down draw method.

A method of manufacturing a chemically strengthened glass plate of the present invention, chemically tempered glass is a glass composition including, in _{mol%, SiO 2 50~80%, Al} 2 O 3 12~18%, Na 2 O 12~20 %, And the molar ratio Na ₂ O / Al ₂ O ₃ is preferably 0.9 to 1.5.

  12thly, it is preferable that the manufacturing method of the chemically strengthened glass plate of this invention uses a chemically strengthened glass plate for a touch panel display.

  In the chemically strengthened glass plate (chemically strengthened glass plate) of the present invention, the plate thickness is 0.4 mm or more and less than 1.0 mm, preferably 0.6 to 0.9 mm, particularly 0.75 to 0.85 mm. It is. When the plate thickness is small, the glass surface is physically stretched by the internal tensile stress after the ion exchange treatment, and the compressive stress value of the surface compressive stress layer becomes small. As a result, the Vickers hardness after the ion exchange treatment Tends to decrease. On the other hand, if the plate thickness is large, the weight of the cover glass becomes heavy, making it difficult to apply to mobile applications.

  In the glass plate for chemical strengthening of the present invention, the Vickers hardness is higher than 500 and lower than 650, preferably 530 to 640, 540 to 630, particularly 550 to 620. If the Vickers hardness before the ion exchange treatment is too low, it becomes difficult to sufficiently increase the Vickers hardness after the ion exchange treatment. On the other hand, if the Vickers hardness before the ion exchange treatment is too high, it becomes difficult to perform cutting processing, end face processing, or the like to a predetermined size before the ion exchange treatment, which may increase the processing cost.

In the glass sheet for chemical strengthening of the present invention, when immersed in KNO ₃ molten salt at 430 ° C. for 4 hours, the Vickers hardness is 700 or more and less than 1100, preferably 710 or more, 720 or more, 730 or more, 740 or more, 750 or more, 760 or more, 770 or more, 780 or more, 790 or more, 800 or more, 810 or more, 820 or more, 830 or more, 840 or more, particularly 850 or more. Further, the chemically strengthened glass plate according to the present invention has a Vickers hardness of 700 or more and less than 1100, preferably 710 or more, 720 or more, 730 or more, 740 or more, 750 or more, 760 or more, 770 or more, 780 or more, 790 or more, 800 or more, 810 or more, 820 or more, 830 or more, 840 or more, particularly 850 or more. When the Vickers hardness after the ion exchange treatment is low, surface scratches recognized by light having high illuminance and parallelism are likely to be attached. On the other hand, if the Vickers hardness after the ion exchange treatment is too high, the tensile stress inside the chemically strengthened glass plate tends to be high, and the chemically strengthened glass plate is likely to be damaged by point collision.

When the chemical strengthening glass plate of the present invention is immersed in KNO ₃ molten salt at 430 ° C. for 4 hours, the compressive stress value of the obtained surface compressive stress layer becomes 1100 MPa or more and less than 1500 MPa. In the chemically strengthened glass plate according to the present invention, the compressive stress value of the surface compressive stress layer is 1100 MPa or more and less than 1500 MPa. The larger the compressive stress value, the higher the Vickers hardness after the ion exchange treatment. However, when an extremely large compressive stress is formed on the glass surface, the internal tensile stress becomes extremely high, and there is a possibility that fragments are scattered when the chemically strengthened glass plate is broken. Therefore, the compressive stress value of the surface compressive stress layer is preferably 1150 MPa or more, 1200 MPa or more, 1250 MPa or more, 1300 MPa or more, particularly 1350 MPa or more. The compressive stress value of the surface compressive stress layer is preferably 1500 MPa or less, 1450 MPa or less, and particularly 1400 MPa or less. Note that if the content of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, ZnO in the glass composition is increased, or the content of SrO, BaO is decreased, the compressive stress value tends to increase. Further, if the ion exchange time is shortened or the temperature of the ion exchange solution is lowered, the compressive stress value tends to increase.

When the glass sheet for chemical strengthening of the present invention is immersed in KNO ₃ molten salt at 430 ° C. for 4 hours, the stress depth of the surface compressive stress layer is preferably 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more. , 35 μm or more, 40 μm or more, particularly 45 μm or more, preferably 100 μm or less, 80 μm or less, particularly 60 μm or less. Further, in the chemically strengthened glass plate according to the present invention, the stress depth of the surface compressive stress layer is preferably 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, particularly 45 μm or more. , Preferably 100 μm or less, 80 μm or less, particularly 60 μm or less. As the stress depth increases, even if the chemically strengthened glass sheet is deeply damaged, the chemically strengthened glass sheet is less likely to break and the variation in mechanical strength is reduced. On the other hand, if the stress depth is too large, the internal tensile stress becomes extremely high, and there is a possibility that fragments are scattered when the chemically strengthened glass plate is broken. In addition, if the content of K ₂ O or P ₂ O _{5 in} the glass composition is increased or the content of SrO or BaO is decreased, the stress depth tends to increase. Moreover, if the ion exchange time is lengthened or the temperature of the ion exchange solution is increased, the stress depth tends to increase.

  In the chemically strengthened glass plate (chemically strengthened glass plate) of the present invention, at least one surface is a polished surface, and preferably both surfaces are polished surfaces. When performing the polishing treatment, the polishing amount (polishing thickness) is preferably 100 nm or more, 500 nm or more, 1 μm or more, 5 μm or more, 10 μm or more, 50 μm or more, and particularly preferably 100 μm or more. The fired surface (molded surface) of glass becomes a heterogeneous layer with a low fictive temperature and few alkali metal oxides. Therefore, when the glass surface is polished, the extraneous layer on the outermost surface disappears, the amount of ion exchange on the outermost surface increases, and the Vickers hardness after the ion exchange treatment can be increased.

  In the chemically strengthened glass plate (chemically strengthened glass plate) of the present invention, the Young's modulus is preferably 65 GPa or more, 69 GPa or more, particularly 71 GPa or more, preferably 90 GPa or less, 85 GPa or less, particularly 80 GPa or less. The higher the Young's modulus, the higher the Vickers hardness. Further, the chemically strengthened glass plate is difficult to bend, and when used for a touch panel display or the like, even if the surface of the chemically strengthened glass plate is strongly pressed with a pen or the like, the amount of deformation of the chemically strengthened glass plate is reduced. As a result, it is easy to prevent the cover glass from coming into contact with the liquid crystal element located on the back surface and causing a display defect. On the other hand, if the Young's modulus is too high, the Vickers hardness before the ion exchange treatment becomes too high, and it becomes difficult to perform cutting, end face processing, etc. to a predetermined size before the ion exchange treatment.

  In the chemically strengthened glass plate (chemically strengthened glass plate) of the present invention, the Poisson's ratio is preferably 0.21 or less, 0.20 or less, particularly 0.19 or less. If the Poisson's ratio is too large, it becomes difficult to change elastically with respect to the stress, so that the depth of the surface flaws tends to be deep, and as a result, visible surface flaws tend to remain.

The glass plate for chemical strengthening (chemically strengthened glass plate) of the present invention contains, as a glass composition, mol%, SiO ₂ 50 to 80%, Al ₂ O ₃ 12 to 18%, Na ₂ O 12 to 20%. The molar ratio Na ₂ O / Al ₂ O ₃ is preferably 0.9 to 1.5. The reason for limiting the content range of each component is shown below. In addition, in description of the containing range of each component,% display points out mol%, unless there is particular notice.

SiO ₂ is a component that forms a network of glass. The content of SiO ₂ is preferably 50 to 80%, 56 to 75%, 60 to 70%, 62 to 69%, particularly 64 to 67%. If the content of SiO ₂ is too small, vitrification becomes difficult, and the thermal expansion coefficient becomes too high, so that the thermal shock resistance tends to decrease. On the other hand, if the content of SiO ₂ is too large, the meltability and moldability tend to be lowered, and the thermal expansion coefficient becomes too low to make it difficult to match the thermal expansion coefficient of the surrounding materials.

Al ₂ O ₃ is a component that increases Vickers hardness, and is a component that increases ion exchange performance, strain point, and Young's modulus. If the content of Al ₂ O ₃ is too small, the scratch resistance tends to be lowered, and the ion exchange performance may not be sufficiently exhibited. Therefore, the preferred lower limit range of Al ₂ O ₃ is 12% or more, 12.5% or more, 13% or more, 14% or more, 14.5% or more, 15% or more, 15.5% or more, 16% or more, 16.1% or more, particularly 16.3% or more. On the other hand, when the content of Al ₂ O ₃ is too large, devitrification crystal glass becomes easy to precipitate, and it becomes difficult to mold the glass sheet by an overflow down draw method or the like. In particular, when an alumina refractory is used as a molded refractory and a glass plate is formed by the overflow down draw method, spinel devitrification crystals are likely to precipitate at the interface with the alumina refractory. In addition, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material. Moreover, acid resistance also falls and it becomes difficult to apply to an acid treatment process. Furthermore, the high-temperature viscosity becomes high and the meltability tends to be lowered. Therefore, a suitable upper limit range of Al ₂ O ₃ is 18% or less, 17.5% or less, particularly 17% or less.

B ₂ O ₃ is a component that reduces high temperature viscosity and density, stabilizes the glass, makes it difficult to precipitate crystals, and lowers the liquidus temperature. However, if the content of B ₂ O ₃ is too large, the stress depth becomes small, or the surface of the glass called burnt is colored due to the ion exchange treatment, and the water resistance tends to decrease. _Thus, preferred range 6% of _{B 2 O 3, 0~5%,} 0~4%, 0~3.5%, 0~3%, 0~2.5%, 0~2%, 0 to 1.5%, 0 to 1%, especially 0 to less than 1%.

Na ₂ O is an ion exchange component, and is a component that lowers the high temperature viscosity and improves the meltability and moldability. Na ₂ O is a component that improves devitrification resistance, particularly reaction devitrification resistance with alumina refractories. When Na 2 _O content is too small, or reduced meltability, lowered coefficient of thermal expansion tends to decrease the ion exchange performance. Therefore, the preferable lower limit range of Na ₂ O is 12% or more, 14% or more, 15% or more, 15.5% or more, particularly 16% or more. On the other hand, when the content of Na ₂ O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance is lowered, and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. In addition, the strain point may be excessively decreased, or the component balance of the glass composition may be lost, and the devitrification resistance may be decreased. Therefore, a preferable upper limit range of Na ₂ O is 20% or less, 19% or less, 18% or less, 17.5% or less, particularly 17% or less.

If the molar ratio Na ₂ O / Al ₂ O ₃ is too small, the meltability is lowered, the devitrification resistance, particularly the reaction devitrification resistance with the alumina refractory is lowered, and the ion exchange performance is likely to be lowered. Become. Therefore, the preferable lower limit range of the molar ratio Na ₂ O / Al ₂ O ₃ is 0.9 or more, 0.95 or more, 0.98 or more, and particularly 1.00 or more. On the other hand, when the molar ratio Na ₂ O / Al ₂ O ₃ is too large, the Vickers hardness and the ion exchange performance tend to be lowered. Therefore, the preferable upper limit range of the molar ratio Na ₂ O / Al ₂ O ₃ is 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.18 or less, 1.15 or less, 13 or less, particularly 1.1 or less.

Suitable content of _{B 2 O 3 + Na 2 O} -Al 2 O 3 is -1.7～2.7%, 0 to 2.55%, 0.5 to 2.4%, especially 0.8 to 2 .2%. This makes it easy to optimize Vickers hardness, meltability, strain point and ion exchange performance. “B ₂ O ₃ + Na ₂ O—Al ₂ O ₃ ” is obtained by subtracting the content of Al ₂ O ₃ from the total amount of B ₂ O ₃ and Na ₂ O.

  In addition to the above components, for example, the following components may be added.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity to increase the meltability and moldability, and also increases the Vickers hardness. Furthermore, Li ₂ O generally has a large effect of increasing the compressive stress value among alkali metal oxides, but in a glass system containing 12% or more of Na ₂ O, the content of Li ₂ O is extremely large. If it becomes, there exists a tendency for a compressive stress value to fall rather. Also the content of Li 2 _O is too large, eluting the ion exchange solution during ion-exchange treatment, there is a possibility to degrade the ion exchange solution. Accordingly, the preferred content of Li ₂ O is 0-2%, 0 to 1.7%, from 0 to 1.5%, 0 to 1%, less than 0 to 1% 0 to 0.5% 0 0.3%, 0-0.1%, especially 0-0.05%.

K ₂ O is a component that promotes ion exchange. Particularly in alkali metal oxides, K ₂ O is a component that decreases the compressive stress value of the surface compressive stress layer and increases the stress depth. Moreover, it is a component which reduces high temperature viscosity and improves a meltability and a moldability. However, if the content of K ₂ O is too large, the thermal expansion coefficient becomes too high, and the thermal shock resistance is lowered or it is difficult to match the thermal expansion coefficient of the surrounding materials. Moreover, there is a tendency that the strain point is excessively lowered and the devitrification resistance is lowered. Therefore, the preferable upper limit range of K ₂ O is 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, particularly less than 2%. Incidentally, when adding _{K 2} O, the preferred amount is 0.1% or more, 0.5% or more, more than 1%, 1.5% or more, particularly 2% or more. In the case of avoiding as much as possible the addition of _{K 2} O is, the preferred content of _{K 2} O 0 to 1%, less than 0 to 1%, in particular 0 to 0.05%.

  MgO is a component that lowers the viscosity at high temperature, increases meltability and formability, and increases the strain point and Vickers hardness. Among alkaline earth metal oxides, MgO is a component that has a large effect on improving ion exchange performance. is there. Therefore, the preferable lower limit range of MgO is 0% or more, 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, 3% .5% or more, particularly 3.7% or more. However, if the content of MgO is too large, the density and thermal expansion coefficient tend to increase, and devitrification resistance, particularly reaction devitrification resistance with alumina refractory, tends to decrease. Therefore, the preferable upper limit range of MgO is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, particularly 4% or less.

  CaO is a component that has a large effect of lowering high temperature viscosity, improving meltability and formability, and increasing strain point and Vickers hardness without lowering devitrification resistance compared to other components. is there. However, when there is too much content of CaO, ion exchange performance will fall or it will become easy to degrade an ion exchange solution at the time of ion exchange processing. Therefore, suitable content of CaO is 0-6%, 0-5%, 0-4%, 0-3.5%, 0-3%, 0-2%, 0-1%, especially 0-0. .5%.

  SrO and BaO are components that lower the viscosity at high temperature to increase the meltability and moldability, and increase the strain point and Young's modulus. However, if their content is excessive, the ion exchange reaction tends to be inhibited. In addition, the density and the coefficient of thermal expansion increase, and the glass tends to devitrify. Therefore, suitable content of SrO and BaO is 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, particularly 0 to 0.1%, respectively. %.

  ZnO is a component that enhances the ion exchange performance, and is a component that is particularly effective in increasing the compressive stress value. Moreover, it is a component which reduces high temperature viscosity, without reducing low temperature viscosity. However, when the content of ZnO is too large, the glass tends to undergo phase separation, the devitrification resistance decreases, the density increases, or the stress depth decreases. Therefore, suitable content of ZnO is 0-6%, 0-5%, 0-3%, especially 0-1%.

The preferred content of B ₂ O ₃ + MgO + ZnO is 0.03 to 3.94%, 0.1 to 3.8%, 0.5 to 3.7%, 1 to 3.5%, especially 2-3. 4%. In this way, it becomes easy to optimize the meltability, devitrification resistance and stress depth. “B ₂ O ₃ + MgO + ZnO” is the total amount of B ₂ O ₃ , MgO and ZnO.

TiO ₂ is a component that enhances ion exchange performance and a component that lowers the high-temperature viscosity. However, if its content is too large, transparency and devitrification resistance are likely to be lowered. Therefore, the content of TiO ₂ is preferably 0 to 4.5%, 0 to less than 1%, 0 to 0.5%, particularly preferably 0 to 0.3%.

ZrO ₂ is a component that increases the Vickers hardness and a component that increases the viscosity and strain point in the vicinity of the liquid phase viscosity. If the content is too large, the devitrification resistance may be significantly reduced. There is also a possibility that the density becomes too high. Accordingly, the preferred content of ZrO ₂ is 0-5% 0-4% 0-3%, in particular 0.001 to 2%.

SnO ₂ is a component that enhances the ion exchange performance, but when its content is too large, the devitrification resistance tends to be lowered. Accordingly, the preferred content of SnO ₂ is 0-3%, 0.01% to 3% 0.05 to 3% 0.1% to 3%, in particular 0.2 to 3%.

P ₂ O ₅ is a component that enhances ion exchange performance, and in particular, a component that increases the stress depth. However, when the content of P ₂ O ₅ is too large, or glass phase separation, the water resistance tends to decrease. Therefore, the suitable content of P ₂ O ₅ is 0 to 10%, 0 to 3%, 0 to 1%, particularly 0 to 0.5%.

As a fining agent, _Cl, SO 3, CeO ₂ group (preferably Cl, SO group ₃₎ one member selected from or two or more may be added 0.001 to 1%.

Suitable content of Fe ₂ O ₃ is less than 1000 ppm (less than 0.1%), less than 800 ppm, less than 600 ppm, less than 400 ppm, especially less than 300 ppm. Further, the Fe ₂ O ₃ content is regulated within the above range, and the molar ratio SnO ₂ / (Fe ₂ O ₃ + SnO ₂ ) is regulated to 0.8 or more, 0.9 or more, and particularly 0.95 or more. It is preferable. If it does in this way, it will become easy to improve the total light transmittance in wavelength 400-770nm and thickness 1mm.

Rare earth oxides such as Nd ₂ O ₃ and La ₂ O ₃ are components that increase Vickers hardness. However, the cost of the raw material itself is high, and when it is added in a large amount, the devitrification resistance tends to be lowered. Therefore, the preferable content of the rare earth oxide is 3% or less, 2% or less, 1% or less, 0.5% or less, particularly 0.1% or less.

Chemically strengthened glass plate of the present invention, from environmental considerations, as a glass composition, substantially _{As 2 O 3, Sb 2 O} 3, PbO, and preferably contains no F. Moreover, environmental considerations, it is also preferable to contain substantially no Bi ₂ O _3. “Substantially free of” means that an explicit component is not actively added as a glass component, but the addition of an impurity level is allowed. Specifically, the content of the explicit component is 0. Indicates the case of less than 05%.

  The method for producing a chemically strengthened glass plate according to the present invention includes forming a molten glass into a plate shape and then cutting it into a predetermined size, whereby the plate thickness is 0.4 mm or more and less than 1.0 mm, and the Vickers hardness is The glass plate preparation step for obtaining a glass plate for chemical strengthening higher than 500 and lower than 650, and the glass plate for chemical strengthening are subjected to ion exchange treatment, and the compressive stress value of the surface compressive stress layer is 1100 MPa or more and less than 1500 MPa. And an ion exchange treatment step for obtaining a chemically strengthened glass plate having a Vickers hardness of 700 or more and less than 1100. The technical features of the method for producing a chemically strengthened glass sheet of the present invention are partially described in the description of the chemically strengthened glass sheet of the present invention. In the present specification, for the sake of convenience, detailed description of the described technical features is omitted.

  In the method for producing a chemically strengthened glass sheet according to the present invention, first, a glass raw material prepared so as to have a desired glass composition is put into a continuous melting furnace, heated and melted at 1500 to 1700 ° C., clarified, and then the molten glass is heated. It is preferable that the sheet is formed into a plate shape after being supplied to the forming apparatus and then cooled. A well-known method can be adopted as a method of cutting into a predetermined dimension after forming into a plate shape.

  In the method for producing a chemically strengthened glass sheet according to the present invention, at the time of forming molten glass, the temperature range between the annealing point and the strain point of the molten glass is cooled at a cooling rate of 3 ° C./min or more and less than 1000 ° C./min. The cooling rate is preferably 10 ° C./min or more, 20 ° C./min or more, 30 ° C./min or more, particularly 50 ° C./min or more, preferably less than 1000 ° C./min, 500 ° C./min. Less than min, especially less than 300 ° C / min. If the cooling rate is too high, the glass structure becomes rough and it becomes difficult to increase the Vickers hardness after the ion exchange treatment. On the other hand, if the cooling rate is too slow, the production efficiency of the chemically strengthened glass plate is lowered. In addition, after shape | molding molten glass in plate shape, you may provide the process of cooling with the said cooling rate separately with respect to the glass plate for chemical strengthening.

  As a method for forming molten glass into a plate shape, it is preferable to employ an overflow down draw method. The overflow downdraw method is a method capable of producing a large number of high-quality glass plates and easily producing a large glass plate. Furthermore, in the overflow downdraw method, alumina or zirconia is used as the molded body refractory. However, the glass sheet for chemical strengthening of the present invention has good compatibility with alumina and zirconia, particularly alumina. It is difficult to react with the green body and to generate bubbles and blisters.

  In addition to the overflow downdraw method, various molding methods can be employed. For example, a forming method such as a float method, a downdraw method (slot downdraw method, redraw method, etc.), a rollout method, a press method, or the like can be employed.

In the method for producing a chemically strengthened glass sheet of the present invention, the conditions for the ion exchange treatment are not particularly limited, and optimum conditions are selected in consideration of the viscosity characteristics, application, thickness, internal tensile stress, dimensional change, etc. of the glass. do it. In particular, when the K ions in the KNO ₃ molten salt are ion exchanged with the Na component in the glass, the surface compressive stress layer can be efficiently formed. In the ion exchange treatment, the temperature of the ion exchange solution is preferably 390 to 480 ° C., and the ion exchange time is preferably 2 to 8 hours. If it does in this way, a surface compression stress layer can be formed efficiently.

  Hereinafter, the present invention will be described based on examples. The following examples are merely illustrative. The present invention is not limited to the following examples.

  Table 1 shows Examples (Sample Nos. 1 to 3 and 7 to 17) and Comparative Examples (Sample Nos. 4 to 6).

  Each sample in the table was prepared as follows. First, glass raw materials were prepared so as to have the glass composition in the table, and were melted at 1650 ° C. for 21 hours using a platinum pot. Subsequently, the molten glass obtained was poured out onto a carbon plate and formed into a flat plate shape, and then the temperature range between the annealing point and the strain point was cooled at 3 ° C./min, and the glass plate for chemical strengthening Got. About the obtained glass plate for chemical strengthening, the surface was optically polished so that plate thickness t = 0.8 mm, and various characteristics were evaluated.

  The density ρ is a value measured by the well-known Archimedes method.

  The strain point Ps and the annealing point Ta are values measured based on the method described in ASTM C336.

  The Vickers hardness Hv is a value measured based on a method based on JIS Z2244 with a measurement load of 100 gf.

  The Young's modulus E is a value measured by a known resonance method.

  The Poisson's ratio is a value calculated by the following mathematical formula. The rigidity G is a value measured by a known resonance method.

[Equation 1]
Poisson's ratio = (E-2G) / 2G
E: Young's modulus (GPa)
G: rigidity (GPa)

Subsequently, both surfaces of each sample were optically polished so as to have a plate thickness in the table. Thereafter, the KNO ₃ molten salt of 430 ° C., by dipping each sample 4 hours, subjected to ion exchange treatment to obtain a chemically tempered glass. Further, after cleaning the surface of each chemically strengthened glass plate, the compressive stress value of the compressive stress layer on the surface is determined from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and the interval between the interference fringes. (CS) and stress depth (DOL) were calculated. In the calculation, the refractive index of each sample was set to 1.50 and the optical elastic constant was set to 30 [(nm / cm) / MPa].

  About each chemically strengthened glass plate, Vickers hardness Hv was measured by the said method.

  The scratch resistance test was conducted as follows. First, silica sand having an average particle size of 50 μm and 1 mg was uniformly placed on each sample, and was injured with a load of 4 kg through a commercially available denim fabric. The scratch was performed only once in one direction, and the distance to be scratched was 1 cm. After scratching the surface of each sample, scratches were observed using a fiber light under the condition of an illuminance of 100,000 lux, and the number of scratches that could be visually confirmed was counted. The test was performed 4 times, and the average value of 4 times was used as the test result.

  As is clear from Table 1, sample No. 1 to 3 and 7 to 17 had Vickers hardness Hv before ion exchange treatment of 550 to 600. Therefore, sample no. 1-3 and 7-17 are considered that the workability before an ion exchange process is favorable. And sample no. 1-3, 7-17, the compression stress value CS of the surface compressive stress layer after the ion exchange treatment is 1100 MPa to 1350 MPa, the Vickers hardness Hv is 710 to 870, and the number of scratches in the scratch resistance test is 8 to 10 there were. Therefore, sample no. 1-3 and 7-17 are considered to have high scratch resistance after the ion exchange treatment. On the other hand, sample No. In Nos. 4 and 5, the compressive stress value CS and Vickers hardness Hv of the surface compressive stress layer after the ion exchange treatment were low, and the number of scratches in the scratch resistance test was also large. Sample No. No. 6 has a Vickers hardness Hv before the ion exchange treatment of 670, so it is considered that the workability before the ion exchange treatment is low.

Sample No. above. Glass raw materials were prepared so as to have the glass compositions according to 1 to 3 and 7 to 17, put into a continuous melting furnace, and formed into a plate shape by an overflow down draw method using an alumina molded body. During molding, the temperature range between the annealing point and the strain point was cooled at 200 ° C./min. The obtained chemically strengthened glass plate was cut into a predetermined size, the surface was optically polished so that the thickness t = 0.8 mm, and then immersed in KNO ₃ molten salt at 430 ° C. for 4 hours. Then, ion exchange treatment was performed to obtain each chemically strengthened glass plate.

  The chemically strengthened glass plate and the chemically strengthened glass plate using the same of the present invention are suitable as a cover glass for a mobile phone, a digital camera, a PDA or the like, or a glass substrate for a touch panel display or the like. Further, the chemically strengthened glass plate of the present invention and the chemically strengthened glass plate using the same are used for applications requiring high mechanical strength, such as window glass, magnetic disk substrates, and flat panel displays. Application to substrate substrates, cover glasses for solar cells, and cover glasses for solid-state imaging devices is expected.

Claims (12)

The plate thickness is 0.4 mm or more and less than 1.0 mm,
Vickers hardness is higher than 500 and lower than 650,
When immersed in KNO ₃ molten salt at 430 ° C. for 4 hours, the resulting surface compressive stress layer has a compressive stress value of 1100 MPa or more and less than 1500 MPa, and a Vickers hardness of 700 or more and less than 1100. Glass plate for chemical strengthening. The glass plate for chemical strengthening according to claim 1, wherein the stress depth of the obtained surface compressive stress layer becomes less than 100 µm when immersed in KNO ₃ molten salt at 430 ° C for 4 hours.   The glass plate for chemical strengthening according to claim 1 or 2, wherein at least one surface is a polished surface.   The glass plate for chemical strengthening according to any one of claims 1 to 3, wherein the glass plate for chemical strengthening has an overflow merging surface at a central portion in a plate thickness direction. As a glass composition, it contains SiO ₂ 50-80%, Al ₂ O ₃ 12-18%, Na ₂ O 12-20% in mol%, and a molar ratio Na ₂ O / Al ₂ O ₃ is 0.9- It is 1.5, The glass plate for chemical strengthening as described in any one of Claims 1-4 characterized by the above-mentioned. After the molten glass is formed into a plate shape, the glass is chemically tempered by cutting it to a predetermined size so that the plate thickness is 0.4 mm or more and less than 1.0 mm, and the Vickers hardness is higher than 500 and lower than 650. A glass plate making process for obtaining a plate;
Ion exchange treatment of the chemically strengthened glass plate to obtain a chemically strengthened glass plate having a compressive stress value of the surface compressive stress layer of 1100 MPa or more and less than 1500 MPa and a Vickers hardness of 700 or more and less than 1100 A process for producing a chemically strengthened glass sheet.   The method for producing a chemically strengthened glass sheet according to claim 6, wherein the chemically strengthened glass sheet is obtained by subjecting the chemically strengthened glass sheet to an ion exchange treatment to obtain a chemically strengthened glass sheet having a stress depth of the surface compressive stress layer of less than 100 µm.   The method for producing a chemically strengthened glass sheet according to claim 6 or 7, further comprising a polishing step of polishing at least one surface of the chemically strengthened glass sheet.   The temperature range between the annealing point and the strain point of the glass sheet for chemical strengthening is cooled at a cooling rate of 3 ° C / min or more and less than 1000 ° C / min when forming the molten glass. The manufacturing method of the chemically strengthened glass plate as described in any one of -8.   Molten glass is shape | molded with the overflow downdraw method, The manufacturing method of the chemically strengthened glass plate as described in any one of Claims 6-9 characterized by the above-mentioned. A chemically strengthened glass plate contains SiO ₂ 50 to 80%, Al ₂ O ₃ 12 to 18%, Na ₂ O 12 to 20% as a glass composition, and a molar ratio Na ₂ O / Al ₂ O. ₃ is 0.9-1.5, The manufacturing method of the chemically strengthened glass plate as described in any one of Claims 6-10 characterized by the above-mentioned.   The method for producing a chemically strengthened glass plate according to any one of claims 6 to 11, wherein the chemically strengthened glass plate is used for a touch panel display.